blob: 534a09e6dc722480d8f46bf960695e3a1177217b [file] [log] [blame]
use core::marker::Unpin;
use core::pin::PinMut;
use futures_core::future::{TryFuture};
use futures_core::stream::{Stream, TryStream};
use futures_core::task::{self, Poll};
use pin_utils::{unsafe_pinned, unsafe_unpinned};
/// A combinator that attempts to filter the results of a stream
/// and simultaneously map them to a different type.
///
/// This structure is returned by the
/// [`try_filter_map`](super::TryStreamExt::try_filter_map) method.
#[derive(Debug)]
#[must_use = "streams do nothing unless polled"]
pub struct TryFilterMap<St, Fut, F> {
stream: St,
f: F,
pending: Option<Fut>,
}
impl<St, Fut, F> Unpin for TryFilterMap<St, Fut, F>
where St: Unpin, Fut: Unpin,
{}
impl<St, Fut, F> TryFilterMap<St, Fut, F> {
unsafe_pinned!(stream: St);
unsafe_unpinned!(f: F);
unsafe_pinned!(pending: Option<Fut>);
pub(super) fn new(stream: St, f: F) -> Self {
TryFilterMap { stream, f, pending: None }
}
/// Acquires a reference to the underlying stream that this combinator is
/// pulling from.
pub fn get_ref(&self) -> &St {
&self.stream
}
/// Acquires a mutable reference to the underlying stream that this
/// combinator is pulling from.
///
/// Note that care must be taken to avoid tampering with the state of the
/// stream which may otherwise confuse this combinator.
pub fn get_mut(&mut self) -> &mut St {
&mut self.stream
}
/// Consumes this combinator, returning the underlying stream.
///
/// Note that this may discard intermediate state of this combinator, so
/// care should be taken to avoid losing resources when this is called.
pub fn into_inner(self) -> St {
self.stream
}
}
impl<St, Fut, F, T> Stream for TryFilterMap<St, Fut, F>
where St: TryStream,
Fut: TryFuture<Ok = Option<T>, Error = St::Error>,
F: FnMut(St::Ok) -> Fut,
{
type Item = Result<T, St::Error>;
fn poll_next(
mut self: PinMut<Self>,
cx: &mut task::Context,
) -> Poll<Option<Result<T, St::Error>>> {
loop {
if self.pending().as_pin_mut().is_none() {
let item = match ready!(self.stream().try_poll_next(cx)) {
Some(Ok(x)) => x,
Some(Err(e)) => return Poll::Ready(Some(Err(e))),
None => return Poll::Ready(None),
};
let fut = (self.f())(item);
PinMut::set(self.pending(), Some(fut));
}
let result = ready!(self.pending().as_pin_mut().unwrap().try_poll(cx));
PinMut::set(self.pending(), None);
match result {
Ok(Some(x)) => return Poll::Ready(Some(Ok(x))),
Err(e) => return Poll::Ready(Some(Err(e))),
Ok(None) => {},
}
}
}
}